Leading article: Time for an investigation into Scotland Yard

Tensions between the heads of big organisations and their successors are hardly unheard of. The departing chief may feel shunted aside, while the incomer aspires to be a "new broom".

Yet the allegations we publish today, apparently showing a concerted campaign to discredit Sir Ian (now Lord) Blair, during his troubled years as Metropolitan Police Commissioner, go far beyond routine resentment and backbiting.

Not only do they illustrate that the Met was a particularly divided organisation, to a degree that cannot but have compromised its effectiveness, they also suggest that some inside the Met made common cause with Rupert Murdoch's News International to undermine Sir Ian's authority.

The unhealthy relationship between NI and some Met officers has been a running theme of the Leveson Inquiry and last week the Independent Police Complaints Commission found the Met had shown poor judgement in recruiting the former deputy editor of the News of the World. Lord Blair is fully justified in wanting an investigation.